From 1cd0cc8fc0f626a3cde1a8dca48d701b9808d6ea Mon Sep 17 00:00:00 2001
From: Peter Petrek <pp313ij@omega.tuke.sk>
Date: Fri, 14 Jan 2022 03:10:57 +0100
Subject: [PATCH] pls

---
 sk1a/maze.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 101 insertions(+), 2 deletions(-)

diff --git a/sk1a/maze.c b/sk1a/maze.c
index 86f3c0c..875b82c 100644
--- a/sk1a/maze.c
+++ b/sk1a/maze.c
@@ -21,12 +21,111 @@ int solve_maze(char* maze, int size) {
     }
 
     printf("\n");
+    char maze2d[size][size];
     for (int y = 0; y < size; y++) {
         for (int x = 0; x < size; x++) {
             printf("%c", maze[size * y + x]);
+            maze2d[y][x] = maze[size * y + x] == 'x' ? 'x' : 0;
         }
         printf("\n");
     }
-    printf("\nend %d\n\n", size);
-    return 0;
+    printf("\nstart %d\n\n", size);
+    
+    int posY = 0, posX = 0;
+
+    while (1) {
+        enum direction next_step;
+
+        if (posX + 1 < size && maze2d[posY][posX + 1] != 'x' && !(maze2d[posY][posX + 1] & CHECKED_BIT)) {
+            next_step = EAST;
+        } else if (posY + 1 < size && maze2d[posY + 1][posX] != 'x' && !(maze2d[posY + 1][posX] & CHECKED_BIT)) {
+            next_step = SOUTH;
+        } else if (posX - 1 >= 0 && maze2d[posY][posX - 1] != 'x' && !(maze2d[posY][posX - 1] & CHECKED_BIT)) {
+            next_step = WEST;
+        } else if (posY - 1 >= 0 && maze2d[posY - 1][posX] != 'x' && !(maze2d[posY - 1][posX] & CHECKED_BIT)) {
+            next_step = NORTH;
+        } else {
+            next_step = NONE;
+        }
+
+        if (next_step != NONE) {
+            maze2d[posY][posX] |= CHECKED_BIT;
+            switch (next_step) {
+                case EAST:
+                    posX += 1;
+                    maze2d[posY][posX] |= WEST;
+                    break;
+                case SOUTH:
+                    posY += 1;
+                    maze2d[posY][posX] |= NORTH;
+                    break;
+                case WEST:
+                    posX -= 1;
+                    maze2d[posY][posX] |= EAST;
+                    break;
+                case NORTH:
+                    posY -= 1;
+                    maze2d[posY][posX] |= SOUTH;
+                    break;
+                default:
+                    break;
+            }
+        } else {
+            char came_from = maze2d[posY][posX] & DIRECTION_BITS;
+            maze2d[posY][posX] = CHECKED_BIT;
+            switch (came_from) {
+                case EAST:
+                    posX += 1;
+                    break;
+                case SOUTH:
+                    posY += 1;
+                    break;
+                case WEST:
+                    posX -= 1;
+                    break;
+                case NORTH:
+                    posY -= 1;
+                    break;
+                default:
+                    break;
+            }
+        }
+
+        if (posX == 0 && posY == 0) {
+            printf("\nend");
+            return 0;
+        } else if (posX == size - 1 && posY == size - 1) {
+            maze2d[0][0] = '*';
+
+            //cleanup data bits
+            for (int y = 0; y < size; y++) {
+                for (int x = 0; x < size; x++) {
+                    if (maze2d[y][x] == CHECKED_BIT || maze2d[y][x] == 0) {
+                        maze2d[y][x] = ' ';
+                    } else if (maze2d[y][x] != 'x') {
+                        maze2d[y][x] = '*';
+                    }
+                }
+            }
+
+            //cleanup redundant routes
+            for (int y = size - 2; y >= 0; y--) {
+                for (int x = size - 2; x >= 0; x--) {
+                    if (maze2d[y][x] == '*' && maze2d[y + 1][x] == '*' && maze2d[y + 1][x + 1] == '*' && maze2d[y][x + 1] == '*') {
+                        maze2d[y + 1][x + 1] = ' ';
+                        maze2d[y][x + 1] = ' ';
+                    }
+                }
+            }
+
+            //serialize
+            for (int y = 0; y < size; y++) {
+                for (int x = 0; x < size; x++) {
+                    maze[y * size + x] = maze2d[y][x];
+                }
+            }
+            printf("\nend");
+            return 1;
+        } 
+    }
 }